A296613 Smallest k such that either k >= n and k is a power of 2, or k >= 5n/3 and the prime divisors of k are precisely 2 and 5.

1, 2, 4, 4, 8, 8, 8, 8, 16, 16, 16, 16, 16, 16, 16, 16, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 128, 128

Offset

1,2

Comments

First disagreement with A062383(n-1) is at n = 129.

For n > 2, a(n) is not squarefree. - Iain Fox, Dec 17 2017

Links

Eric M. Schmidt, Table of n, a(n) for n = 1..10000

Bernadette Faye, Florian Luca, Pieter Moree, On the discriminator of Lucas sequences, arXiv:1708.03563 [math.NT], 2017, Theorem 1.

Prog

(PARI) a(n) = for(k=n, +oo, if(k == 2^valuation(k, 2) || (k >= 5*n/3 && factor(k)[, 1] == [2, 5]~), return(k))) \\ Iain Fox, Dec 17 2017

Crossrefs

Cf. A033846.

Sequence in context: A265544 A290221 A098820 * A062383 A034583 A076347

Adjacent sequences: A296610 A296611 A296612 * A296614 A296615 A296616

Keyword

nonn

Author

Eric M. Schmidt, Dec 16 2017

Status

approved